1. Field of the Invention
The present invention relates to techniques for determining fluid parameters. More particularly, the present invention relates to techniques for determining downhole fluid parameters, such as fluid direction and fluid velocity.
2. Background of the Related Art
Oil rigs are positioned at wellsites for performing a variety of oilfield operations, such as drilling a well, performing downhole testing and producing located hydrocarbons. Downhole drilling tools are advanced into the earth from a surface rig to form a well. During or after drilling, casing is typically cemented into place to line at least a portion of the well. Once the well is formed, production tools may be positioned about the well to draw fluids to the surface.
Oilfield operations are generally complicated, time consuming and very expensive endeavors. In recognition of these expenses, added emphasis has been placed on well logging, profiling and monitoring of well conditions. Over the years, the detecting and monitoring of well conditions has become a more sophisticated and critical part of managing well operations. During these operations, initial gathering of information relative to well and surrounding formation conditions may be obtained by running a logging tool into the well. The logging tool may be configured to acquire temperature, pressure, acidity, viscosity, resistivity, composition, and/or other downhole parameters that provide well condition information. A map of the acquired information may be generated, resulting in an overall profile of the well which may be of great value in subsequent monitoring and servicing of the well.
The oilfield operations often involve servicing of the well by way of coiled tubing applications, particularly in the case of deviated wells. Coiled tubing applications involve the deployment of a string of coiled tubing, which is capable of delivering treatment fluids and carrying out a variety of downhole servicing applications, into the well. It may be useful, during such operations, to know various downhole parameters. In particular, knowledge of characteristics of various downhole fluids, such as hydrocarbons, water, drilling muds, gases, etc., and fluid parameters relating thereto, such as temperature and pressure, may be useful in monitoring performance, safety, characteristics, etc. In particular, knowledge of fluid and other parameters may be used to assist in locating and treating subsurface reservoirs containing valuable hydrocarbons. Reservoir treatment may involve, for example, production logging (PL) and/or fluid diversion & placement.
In order to determine downhole fluid parameters, fluid sensors are often used to take fluid measurements. Examples of fluid sensors that have been used are spinners, electromagnetic (EM) flow meters, ultrasonic flow meters (Doppler based), and various kinds of tracers (e.g. radioactive). In some cases, fluid sensors may be thermal based sensors, such as time of flight, anemometry, calorimetric, etc. Examples of existing fluid sensors and/or measurement techniques are described in Patent/Application Nos. US20090204346, US20090090176, U.S. Pat. No. 6,801,039, US20090153155, US20090266175, US20090038410, US20100089571, US20090271129, U.S. Pat. No. 7,644,611, U.S. Pat. No. 7,637,167, U.S. Pat. No. 7,258,005, U.S. Pat. No. 6,832,527, U.S. Pat. No. 5,457,396, U.S. Pat. No. 6,527,923, U.S. Pat. No. 4,608,983, DE3213902, DE3820025, DE4017877, EP592888 and EP 0908712. Some cases involve the use of fluid sensors to measure fluid flow rates as described, for example, in GB Patent Application Nos. 2159631 and 2201001. Other cases involve the use of fluid sensors in downhole applications as described, for example, in US Patent/Application Nos. 20100084132, U.S. Pat. Nos. 7,707,898, 6,860,325, and 6,854,341.
Despite the development of techniques for measuring fluids using fluid sensors, there remains a need to provide advanced techniques for determining fluid parameters usable in downhole applications. It may be desirable to provide techniques that determine fluid parameters relating to fluid flow. It may be further desirable to provide techniques that are capable of taking accurate measurements, even in difficult conditions (e.g, harsh conditions, low flow rates, etc.) Preferably, such techniques involve one or more of the following, among others: accuracy of measurements, optimized measurement processes, minimized components, reduced size, robust capabilities, reliability, operability in even harsh downhole conditions, non-intrusive positioning, good response at even very low flow rates & velocities, detection of flow parameters over full range of measurement, simple packaging, resistance to aggressive media (e.g, acid and downhole conditions), measurement methodologies tailored to the equipment used, adjustability to sensor size, operability in downhole conditions (e.g., at high temperatures and/or pressures), etc. The present invention is directed at achieving these needs.